1. Field of the Invention
This invention relates to circuit breakers and more particularly to a circuit breaker actuated by a shape memory alloy wherein, when a voltage applied to a device being protected, such as an electric circuit and electric element, reaches a predetermined value or more, circuit breaking action is performed.
2. Prior Art
A known circuit breaker has been developed in which the circuit breaker is connected in series with the device being protected and, when an electric current through the device protected reaches a predetermined value or more, the current is interrupted.
Such a conventional breaker has shortcomings as follows.
First, in certain types of circuits the relationship between the current and the voltage is not always predetermined, i.e. certain voltage can bring about various current values. Hence, in case where an overvoltage on the device being protected is to be prevented by a conventional circuit breaker, the circuit breaking action cannot always be performed accurately at a desired critical voltage.
Next, even under normal conditions, current passes through the circuit breaker, thereby causing electric power to be consumed therein to some degree.
Further, a relatively high current high is needed to actuate the circuit breaker.
Yet further, the circuit breaker is complicated in construction and high in manufacturing cost.